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Refactor out MaxPossibleReward, fix staking arithmetic (#4041)

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* Refactor out MaxPossibleReward, fix staking arithmetic

* Fix rounding error in test
This commit is contained in:
Gavin Wood
2019-11-07 12:34:13 +01:00
committed by GitHub
parent dcee91412c
commit bb6b3db57e
6 changed files with 52 additions and 44 deletions
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substrate/core/sr-primitives/src/curve.rs
+5 -2
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@@ -23,7 +23,9 @@ use core::ops::Sub;
#[derive(PartialEq, Eq, primitives::RuntimeDebug)] #[derive(PartialEq, Eq, primitives::RuntimeDebug)]
pub struct PiecewiseLinear<'a> { pub struct PiecewiseLinear<'a> {
/// Array of points. Must be in order from the lowest abscissas to the highest. /// Array of points. Must be in order from the lowest abscissas to the highest.
pub points: &'a [(Perbill, Perbill)] pub points: &'a [(Perbill, Perbill)],
/// The maximum value that can be returned.
pub maximum: Perbill,
} }
fn abs_sub<N: Ord + Sub<Output=N> + Clone>(a: N, b: N) -> N where { fn abs_sub<N: Ord + Sub<Output=N> + Clone>(a: N, b: N) -> N where {
@@ -135,7 +137,8 @@ fn test_calculate_for_fraction_times_denominator() {
(Perbill::from_parts(0_000_000_000), Perbill::from_parts(0_500_000_000)), (Perbill::from_parts(0_000_000_000), Perbill::from_parts(0_500_000_000)),
(Perbill::from_parts(0_500_000_000), Perbill::from_parts(1_000_000_000)), (Perbill::from_parts(0_500_000_000), Perbill::from_parts(1_000_000_000)),
(Perbill::from_parts(1_000_000_000), Perbill::from_parts(0_000_000_000)), (Perbill::from_parts(1_000_000_000), Perbill::from_parts(0_000_000_000)),
] ],
maximum: Perbill::from_parts(1_000_000_000),
}; };
pub fn formal_calculate_for_fraction_times_denominator(n: u64, d: u64) -> u64 { pub fn formal_calculate_for_fraction_times_denominator(n: u64, d: u64) -> u64 {
substrate/node/runtime/src/lib.rs
+1 -4
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@@ -241,7 +241,7 @@ impl session::historical::Trait for Runtime {
srml_staking_reward_curve::build! { srml_staking_reward_curve::build! {
const REWARD_CURVE: PiecewiseLinear<'static> = curve!( const REWARD_CURVE: PiecewiseLinear<'static> = curve!(
min_inflation: 0_025_000, min_inflation: 0_025_000,
max_inflation: 0_100_000, // 10% - must be equal to MaxReward below. max_inflation: 0_100_000,
ideal_stake: 0_500_000, ideal_stake: 0_500_000,
falloff: 0_050_000, falloff: 0_050_000,
max_piece_count: 40, max_piece_count: 40,
@@ -253,8 +253,6 @@ parameter_types! {
pub const SessionsPerEra: sr_staking_primitives::SessionIndex = 6; pub const SessionsPerEra: sr_staking_primitives::SessionIndex = 6;
pub const BondingDuration: staking::EraIndex = 24 * 28; pub const BondingDuration: staking::EraIndex = 24 * 28;
pub const RewardCurve: &'static PiecewiseLinear<'static> = &REWARD_CURVE; pub const RewardCurve: &'static PiecewiseLinear<'static> = &REWARD_CURVE;
pub const MaxReward: Perbill = Perbill::from_percent(10);
// ^^^ 10% - must be equal to max_inflation, above.
} }
impl staking::Trait for Runtime { impl staking::Trait for Runtime {
@@ -269,7 +267,6 @@ impl staking::Trait for Runtime {
type BondingDuration = BondingDuration; type BondingDuration = BondingDuration;
type SessionInterface = Self; type SessionInterface = Self;
type RewardCurve = RewardCurve; type RewardCurve = RewardCurve;
type MaxPossibleReward = MaxReward;
} }
parameter_types! { parameter_types! {
substrate/srml/staking/reward-curve/src/lib.rs
+9
View File
@@ -323,6 +323,14 @@ fn compute_points(input: &INposInput) -> Vec<(u32, u32)> {
fn generate_piecewise_linear(points: Vec<(u32, u32)>) -> TokenStream2 { fn generate_piecewise_linear(points: Vec<(u32, u32)>) -> TokenStream2 {
let mut points_tokens = quote!(); let mut points_tokens = quote!();
let max = points.iter()
.map(|&(_, x)| x)
.max()
.unwrap_or(0)
.checked_mul(1_000)
// clip at 1.0 for sanity only since it'll panic later if too high.
.unwrap_or(1_000_000_000);
for (x, y) in points { for (x, y) in points {
let error = || panic!(format!( let error = || panic!(format!(
"Generated reward curve approximation doesn't fit into [0, 1] -> [0, 1] \ "Generated reward curve approximation doesn't fit into [0, 1] -> [0, 1] \
@@ -346,6 +354,7 @@ fn generate_piecewise_linear(points: Vec<(u32, u32)>) -> TokenStream2 {
quote!( quote!(
_sr_primitives::curve::PiecewiseLinear::<'static> { _sr_primitives::curve::PiecewiseLinear::<'static> {
points: & [ #points_tokens ], points: & [ #points_tokens ],
maximum: _sr_primitives::Perbill::from_parts(#max),
} }
) )
} }
substrate/srml/staking/src/inflation.rs
+29 -20
View File
@@ -32,13 +32,17 @@ pub fn compute_total_payout<N>(
npos_token_staked: N, npos_token_staked: N,
total_tokens: N, total_tokens: N,
era_duration: u64 era_duration: u64
) -> N where N: SimpleArithmetic + Clone ) -> (N, N) where N: SimpleArithmetic + Clone {
{
// Milliseconds per year for the Julian year (365.25 days). // Milliseconds per year for the Julian year (365.25 days).
const MILLISECONDS_PER_YEAR: u64 = 1000 * 3600 * 24 * 36525 / 100; const MILLISECONDS_PER_YEAR: u64 = 1000 * 3600 * 24 * 36525 / 100;
Perbill::from_rational_approximation(era_duration as u64, MILLISECONDS_PER_YEAR) let portion = Perbill::from_rational_approximation(era_duration as u64, MILLISECONDS_PER_YEAR);
* yearly_inflation.calculate_for_fraction_times_denominator(npos_token_staked, total_tokens) let payout = portion * yearly_inflation.calculate_for_fraction_times_denominator(
npos_token_staked,
total_tokens.clone(),
);
let maximum = portion * (yearly_inflation.maximum * total_tokens);
(payout, maximum)
} }
#[cfg(test)] #[cfg(test)]
@@ -59,26 +63,31 @@ mod test {
#[test] #[test]
fn npos_curve_is_sensible() { fn npos_curve_is_sensible() {
const YEAR: u64 = 365 * 24 * 60 * 60 * 1000; const YEAR: u64 = 365 * 24 * 60 * 60 * 1000;
// check maximum inflation.
// not 10_000 due to rounding error.
assert_eq!(super::compute_total_payout(&I_NPOS, 0, 100_000u64, YEAR).1, 9_993);
//super::I_NPOS.calculate_for_fraction_times_denominator(25, 100) //super::I_NPOS.calculate_for_fraction_times_denominator(25, 100)
assert_eq!(super::compute_total_payout(&I_NPOS, 0, 100_000u64, YEAR), 2_498); assert_eq!(super::compute_total_payout(&I_NPOS, 0, 100_000u64, YEAR).0, 2_498);
assert_eq!(super::compute_total_payout(&I_NPOS, 5_000, 100_000u64, YEAR), 3_248); assert_eq!(super::compute_total_payout(&I_NPOS, 5_000, 100_000u64, YEAR).0, 3_248);
assert_eq!(super::compute_total_payout(&I_NPOS, 25_000, 100_000u64, YEAR), 6_246); assert_eq!(super::compute_total_payout(&I_NPOS, 25_000, 100_000u64, YEAR).0, 6_246);
assert_eq!(super::compute_total_payout(&I_NPOS, 40_000, 100_000u64, YEAR), 8_494); assert_eq!(super::compute_total_payout(&I_NPOS, 40_000, 100_000u64, YEAR).0, 8_494);
assert_eq!(super::compute_total_payout(&I_NPOS, 50_000, 100_000u64, YEAR), 9_993); assert_eq!(super::compute_total_payout(&I_NPOS, 50_000, 100_000u64, YEAR).0, 9_993);
assert_eq!(super::compute_total_payout(&I_NPOS, 60_000, 100_000u64, YEAR), 4_379); assert_eq!(super::compute_total_payout(&I_NPOS, 60_000, 100_000u64, YEAR).0, 4_379);
assert_eq!(super::compute_total_payout(&I_NPOS, 75_000, 100_000u64, YEAR), 2_733); assert_eq!(super::compute_total_payout(&I_NPOS, 75_000, 100_000u64, YEAR).0, 2_733);
assert_eq!(super::compute_total_payout(&I_NPOS, 95_000, 100_000u64, YEAR), 2_513); assert_eq!(super::compute_total_payout(&I_NPOS, 95_000, 100_000u64, YEAR).0, 2_513);
assert_eq!(super::compute_total_payout(&I_NPOS, 100_000, 100_000u64, YEAR), 2_505); assert_eq!(super::compute_total_payout(&I_NPOS, 100_000, 100_000u64, YEAR).0, 2_505);
const DAY: u64 = 24 * 60 * 60 * 1000; const DAY: u64 = 24 * 60 * 60 * 1000;
assert_eq!(super::compute_total_payout(&I_NPOS, 25_000, 100_000u64, DAY), 17); assert_eq!(super::compute_total_payout(&I_NPOS, 25_000, 100_000u64, DAY).0, 17);
assert_eq!(super::compute_total_payout(&I_NPOS, 50_000, 100_000u64, DAY), 27); assert_eq!(super::compute_total_payout(&I_NPOS, 50_000, 100_000u64, DAY).0, 27);
assert_eq!(super::compute_total_payout(&I_NPOS, 75_000, 100_000u64, DAY), 7); assert_eq!(super::compute_total_payout(&I_NPOS, 75_000, 100_000u64, DAY).0, 7);
const SIX_HOURS: u64 = 6 * 60 * 60 * 1000; const SIX_HOURS: u64 = 6 * 60 * 60 * 1000;
assert_eq!(super::compute_total_payout(&I_NPOS, 25_000, 100_000u64, SIX_HOURS), 4); assert_eq!(super::compute_total_payout(&I_NPOS, 25_000, 100_000u64, SIX_HOURS).0, 4);
assert_eq!(super::compute_total_payout(&I_NPOS, 50_000, 100_000u64, SIX_HOURS), 7); assert_eq!(super::compute_total_payout(&I_NPOS, 50_000, 100_000u64, SIX_HOURS).0, 7);
assert_eq!(super::compute_total_payout(&I_NPOS, 75_000, 100_000u64, SIX_HOURS), 2); assert_eq!(super::compute_total_payout(&I_NPOS, 75_000, 100_000u64, SIX_HOURS).0, 2);
const HOUR: u64 = 60 * 60 * 1000; const HOUR: u64 = 60 * 60 * 1000;
assert_eq!( assert_eq!(
@@ -87,7 +96,7 @@ mod test {
2_500_000_000_000_000_000_000_000_000u128, 2_500_000_000_000_000_000_000_000_000u128,
5_000_000_000_000_000_000_000_000_000u128, 5_000_000_000_000_000_000_000_000_000u128,
HOUR HOUR
), ).0,
57_038_500_000_000_000_000_000 57_038_500_000_000_000_000_000
); );
} }
substrate/srml/staking/src/lib.rs
+6 -12
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@@ -524,10 +524,6 @@ pub trait Trait: system::Trait {
/// The NPoS reward curve to use. /// The NPoS reward curve to use.
type RewardCurve: Get<&'static PiecewiseLinear<'static>>; type RewardCurve: Get<&'static PiecewiseLinear<'static>>;
/// The maximum possible reward (in proportion of total issued tokens) that can be paid in one
/// reward cycle.
type MaxPossibleReward: Get<Perbill>;
} }
/// Mode of era-forcing. /// Mode of era-forcing.
@@ -1203,7 +1199,7 @@ impl<T: Trait> Module<T> {
let validator_len: BalanceOf<T> = (validators.len() as u32).into(); let validator_len: BalanceOf<T> = (validators.len() as u32).into();
let total_rewarded_stake = Self::slot_stake() * validator_len; let total_rewarded_stake = Self::slot_stake() * validator_len;
let total_payout = inflation::compute_total_payout( let (total_payout, max_payout) = inflation::compute_total_payout(
&T::RewardCurve::get(), &T::RewardCurve::get(),
total_rewarded_stake.clone(), total_rewarded_stake.clone(),
T::Currency::total_issuance(), T::Currency::total_issuance(),
@@ -1220,16 +1216,14 @@ impl<T: Trait> Module<T> {
} }
} }
let total_reward = total_imbalance.peek(); // assert!(total_imbalance.peek() == total_payout)
// assert!(total_reward <= total_payout) let total_payout = total_imbalance.peek();
let max_reward = T::MaxPossibleReward::get() * T::Currency::total_issuance(); let rest = max_payout.saturating_sub(total_payout);
let rest_reward = max_reward.saturating_sub(total_reward); Self::deposit_event(RawEvent::Reward(total_payout, rest));
Self::deposit_event(RawEvent::Reward(total_reward, rest_reward));
T::Reward::on_unbalanced(total_imbalance); T::Reward::on_unbalanced(total_imbalance);
T::RewardRemainder::on_unbalanced(T::Currency::issue(rest_reward)); T::RewardRemainder::on_unbalanced(T::Currency::issue(rest));
} }
// Increment current era. // Increment current era.
substrate/srml/staking/src/mock.rs
+2 -6
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@@ -192,7 +192,6 @@ parameter_types! {
pub const SessionsPerEra: SessionIndex = 3; pub const SessionsPerEra: SessionIndex = 3;
pub const BondingDuration: EraIndex = 3; pub const BondingDuration: EraIndex = 3;
pub const RewardCurve: &'static PiecewiseLinear<'static> = &I_NPOS; pub const RewardCurve: &'static PiecewiseLinear<'static> = &I_NPOS;
pub const MaxReward: Perbill = Perbill::from_percent(10);
} }
impl Trait for Test { impl Trait for Test {
type Currency = balances::Module<Self>; type Currency = balances::Module<Self>;
@@ -206,7 +205,6 @@ impl Trait for Test {
type BondingDuration = BondingDuration; type BondingDuration = BondingDuration;
type SessionInterface = Self; type SessionInterface = Self;
type RewardCurve = RewardCurve; type RewardCurve = RewardCurve;
type MaxPossibleReward = MaxReward;
} }
pub struct ExtBuilder { pub struct ExtBuilder {
@@ -434,14 +432,12 @@ pub fn start_era(era_index: EraIndex) {
} }
pub fn current_total_payout_for_duration(duration: u64) -> u64 { pub fn current_total_payout_for_duration(duration: u64) -> u64 {
let res = inflation::compute_total_payout( inflation::compute_total_payout(
<Test as Trait>::RewardCurve::get(), <Test as Trait>::RewardCurve::get(),
<Module<Test>>::slot_stake() * 2, <Module<Test>>::slot_stake() * 2,
Balances::total_issuance(), Balances::total_issuance(),
duration, duration,
); ).0
res
} }
pub fn reward_all_elected() { pub fn reward_all_elected() {